Metal blackening composition and method



Patented May 25, 1954 OFFICE METAL BLACKENING COMPOSITION AND METHODJoseph C. Singler, Cleveland, Ohio N 0 Drawing.

This invention relates to metal blackening and especially tocompositions and methods for use in blackening metals bydipping orplating processes.

Heretofore there have been some efforts made to provide blackenedfinishes on metals for some uses, but mostly such black finishes would.not have sufiicient adherence to the base metal as to be satisfactory.Furthermore, not all metals could be blackened. Thus previouscompositions and methods for blackening metals have, insofar as I amaware, not been completely satisfactory for one or more reasons.

The general object of the present invention is to provide a novel metalblackening composition which is characterized by its ability to producea desirable black finish upon metals with the finish being permanentlybonded to the base metal.

Another object of the invention is to provide a basic composition whichcan be varied slightly to make it adaptable for use in blackeningcertain special metals by dipping or plating operations.

Another object of the invention is to provide a metal blackeningcomposition for treating substantially any metal to give it a permanentblack surface.

Yet another object of the invention is to provide a relativelyinexpensive composition and method for use in blackening metals.

The foregoing and other objects and advantages of the invention will bemade more apparent as the specification proceeds.

The present invention broadly relates to a new composition for use inblackening substantially any and all metals, such as brass, copper,nickel, stainless steel, aluminum, zinc or cadmium, or alloys of suchmetals, by a dipping or plating process, and this composition basicallycomprises relatively large amounts of nickel and ammonium chlorides andsmall amounts of Rochelle salt and zinc chloride.

Example I One specific composition that has been particularly suitablefor blackening stainless steel is one which includes the followingmaterials in the quantities (dry weight) indicated:

About 4 oz. of ammonium chloride;

About 8 02. of nickel chloride;

About 1 oz. of Rochelle salt;

About oz. of zinc chloride;

About 2 oz. of sodium chloride;

About oz. of ammonium molybdate; and About 1 gal. of water.

Application January 21, 1952, Serial No. 267,509

4 Claims. (01. 204-43) Of the materials listed, the ammonium molybdateseems to be vital to the composition for blackening cadmium by dipping,but a small amount of ammonium molybdate aids in securing the actiondesired in blackening other metals by an electroplating action. Ingeneral, the molybdate appears to speed up the blackening action andgive a deep black color on the finished product.

It appears that a small amount of sodium chloride is present in thecomposition primarily as an electrical conductor but it also aids inobtaining the action desired.

Example II Another illustration of my composition with the limits ofvariation in the quantities of materials (dry weight) used forblackening metals such as stainless steel, brass, copper, steel,aluminum and cadmium, or their alloys, would be as follows:

Nickel chloride About 6 to 12 oz. Ammonium chloride About 3 to 6 oz.Rochelle salt About to 1 oz. Zinc chloride About to 1 oz. Sodiumchloride About 1 to 3 oz. Ammonium molybdate About A; oz. Water 1 gallonThe foregoing composition has given excellent results in providing adesirable blackening action on most metals and their alloys. Thecomposition even is satisfactory for use in treating stainless steel.Variations in the compositions within the limits stated vary the speedof the action slightly but do not materially alter the action secured.

Zinc articles can be coated by use of my novel composition by eitherdipping the zinc articles in baskets or by an electroplating process,and cadmium articles can be similarly processed.

Of course, any desired quantity of solution could be made as long as theproportions stated are maintained.

When blackening steel, stainless steel, brass, copper, aluminum ornickel articles, or alloys of such metal, and also for cadmium plated orfinished articles, it is very desirable that an electroplating processbe used to obtain the desired black finish. Thus, in barrel plating, Imight use between 6 and 9 volts with amperes of electrical energyflowing through the plating solution. In still plating, only about 4 to6 volts would be required with about the same amperage of current flow.

It will be appreciated that before articles are blackened by my improvedprocess, these articles 3 should be cleaned by dipping them inconventional cleaning solutions maintained at about 140 F. The articlesnext would be washed thoroughly in water before being blackened.

When blackening articles by electroplating in accordance with theinvention, the articles are the cathodes and the anodes are made fromstainless steel or, preferably, nickel.

The specific composition set forth in Example I has given particularlygood results on metal articles made from the metals indicated, or with afinish surface of such metals. A very black, tightly bonded coat isobtained in only a few minutes by practice of the invention.

While two complete embodiments of the invention have been disclosedherein, it will be appreciated that modifications of these particularembodiments of the invention may be resorted to without departing fromthe scop of the invention as defined by the appended claims.

Having thus described my invention, claim is:

1. A composition for blackening metals of the class consisting of brass,copper, nickel, steel, aluminum, zinc, stainless steel, and cadmium byan electroplating process, which composition consists essentially of bydry weight, about 8 parts nickel chloride, about 4 parts of ammoniumchloride, about 1 part of Rochelle salt, about part of zinc chloride,about 2 parts of sodium chloride, about part of ammonium molybdate, andwater.

2. A composition for blackening cadmium by a what I dipping process,which composition consists essentially of by dry weight, about 8 partsnickel chloride, about 4 parts of ammonium chloride, about 1 part ofRochelle salt, about parts of zinc chloride, about 2 parts of sodiumchloride and a small amount of ammonium molybdate, and water.

3. A composition for use in blackening metals, which compositionconsists essentially of by dry weight about 6 to 12 parts nickelchloride, about 3 to 6 parts ammonium chloride, about to 1 /2 parts ofRochelle salt, about to 1 part zinc chloride, about 1 to 3 parts sodiumchloride, at small quantity of ammonium molybdate, and water.

4. A process of blackening a metal surface from the class consisting ofsteel, brass, copper, aluminum, nickel and cadmium comprising immersingthe metal surface in a water bath consisting essentially of per gallonof water about 8 oz. nickel chloride; about 4 oz. of ammonium chloride;about 1 oz. of Rochelle salt; about oz. of zinc chloride; about 2 oz. ofsodium chloride; and about oz. of ammonium molybdate, and passing a lowvoltage electrical current therethrough with the metal as the cathode.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,080,520 Westbrook May 18, 1937 2,228,99 Freed Jan. 14, 19412,415,651 Nechamkin Feb. 11, 1947

4. A PROCESS OF BLACKENING A METAL SURFACE FROM THE CLASS CONSISTING OFSTEEL, BRASS, COPPER, ALUMINUM, NICKEL AND CADMIUM COMPRISING IMMERSINGTHE METAL SURFACE IN A WATER BATH CONSISTING ESSENTIALLY OF PER GALLONOF WATER ABOUT 8 OZ. NICKEL CHLORIDE; ABOUT 4 OZ. AMMONIUM CHLORIDE;ABOUT 1 OZ. OF ROCHELLE SALT; ABOUT 3/4 OZ. OF ZINC CHLORIDE; ABOUT 2OZ. OF SODIUM CHLORIDE; AND ABOUT 1/4 OZ. OF AMMONIUM, MOLYBDATE, ANDPASSING A LOW VOLTAGE ELECTRICAL CURRENT THERETHROUGH WITH THE METAL ASTHE CATHODE.